Okay, in answer to my own question, there were 193 Rowlands in Caernarvonshire in the 1841 census, so I suppose it wasn't an entirely uncommon name. 77 Moses(es).
The reason I was interested in William William's Rowland is that one of the children (pictured at top of page) who emigrated to Patagonia named a son Rowland. I have noticed that names tend to go around in families, so I wondered if there was a connection.
I was dreaming last night that the Williamses were descended from Macsen Wledig. No idea where that came from, and as I frequently remind my husband,
I am not responsible for the content of my dreams. 
Cheers,
C